The invention relates to a gas turbine compressor comprising a compressor housing, guide vanes, rotor blades, valve-controlled blow-in openings for stabilizing the compressor flow and at least one valve for controlling the quantity of air blown in via the blow-in openings.
Compressors may begin to pump under certain operating conditions (throttling). Typically, the pumping is produced from an unstable flow condition. This state can occur especially in a partial load range (off-design state). The gas turbine compressor is designed for specific flight conditions, in which it must generate the pre-calculated characteristic values such as throughput, compression ratio, efficiency, etc. But even beyond these design items, the compressor must possess still acceptable and safe operating behavior, for example, on the landing approach of an aircraft, where quick thrust changes and thus quick changes in speed are required for adhering to a glide path. But even when starting up in the lower speed range, the compressor must make sure that the flow is smooth and must enable rapid acceleration to full load.
Of course, the characteristic curve of a compressor is also measured in the partial load range. To determine a safe operating range, the so-called travel line must connect the operating points on the various speed lines to one another, possess an adequate safety margin from the so-called pumping limit, at which, as already stated, a flow separation occurs on the compressor blades.
There have already been attempts in the past to shift the pumping limit as far as possible towards low throughputs in order to be able to bring the travel line into other ranges or to establish a still greater distance from the pumping limit.
Solutions in the prior art are in particular blowing air into the housing or rotor region of a compressor under certain operating conditions. This lateral blowing of air in the direction of rotor blades is supposed to stabilize the flow in the compressor.
The blowing in of air can be stationary (without changing the mass flow of blown-in air) or be controlled with the aid of valves, wherein the latter is described in German Patent Document No. DE 10 2005 052 466 A1 and U.S. Pat. No. 6,125,626.
The object of the invention is improving the stabilization of the flow in the region of the rotor blades even further.
To this end, the inventive gas turbine compressor of the type mentioned at the outset provides that at least one pressure sensor coupled with the control mechanism of the valve be provided in the region of the rotor blades for detecting the pressure in the compressor, wherein the valve can be controlled as a function of the pressure detected.
Whereas the possible operating conditions in the compressor are computed via algorithms in the prior art, the invention provides for detecting the actual pressure via pressure sensors in the crucial regions, namely in the region of the rotor blades, and controlling the inflow of air so to speak as a function of the actual value in practice rather than the theoretical value.
Several pressure sensors distributed over the circumference of the flow channel (annular channel between the rotor and outer housing) are preferably provided. These pressure sensors are situated so to speak on a type of ring.
According to the preferred embodiment, several pressure sensors distributed over the circumference of the flow channel are even provided upstream and downstream from the blow-in openings so that the pressures before and after introducing the additional air may be detected, which is even more effective.
The blow-in openings should be arranged directly upstream from the rotor blades.
Because there are flow conditions in which modular circumferential disturbances occur during pumping, it is advantageous that every blow-in opening be assigned its own valve.
Of course, several blow-in openings may have one of numerous valves in order to save on components and costs.
Continuous, modulated or pulsed flows may be achieved using the numerous valves assigned to the blow-in openings.
Modular circumferential disturbances may be extinguished so to speak by targeted anti-phase blow-in such as with anti-noise. Of course, brief, peak-like disturbances may also be effectively corrected by a quick, complete opening of one or more valves.
The valve(s) are microvalves, in particular based on MEMS technology.
These types of valves are characterized by a rapid switchability and for the most part have an external actuator, which can allow the valve to also modulate/vibrate (e.g., at 400 Hz).
The control mechanism for the pressure sensors may be integrated into the respective pressure sensor itself so that a pressure sensor is assigned to one or more valves and controls these directly, or a central control mechanism may be provided.
The actuators are solenoids or piezo elements in particular.
The valves as well as the blow-in openings are situated in particular in the outer housing, wherein, however, an inflow in the hub region is also possible as an alternative.
Furthermore, the invention creates a method for stabilizing the gas turbine compressor flow by means of an electric control mechanism, which is coupled with several valves on inflow openings provided on the circumference of the flow channel. The method according to the invention provides that the pressure conditions in the flow channel are detected and the valves are controlled as a function thereof. Detection is accomplished directly via the pressure sensors.
The pressure conditions are detected in particular upstream and/or downstream from the inflow openings.
As already explained, the valves may be optionally opened continuously, in a modulated manner or in a pulsed manner; the control mechanism permits all these possibilities.
Additional features and advantages of the invention are disclosed in the following description and in the following drawings to which reference is made.